1. Field of the Invention
The present invention relates to a recording head element substrate having electricity-heat converters and recording function elements formed on the substrate, an ink jet head using the recording head element substrate, an ink jet head cartridge thereof, and an ink jet apparatus which adopts the ink jet head, and is useful for an output printer or video output printer for a copying machine, a facsimile, a word processor, and a host computer.
2. Related Background Art
Conventionally, the constitution of recording heads has been made such that an array of electricity-heat conversion elements is formed on a single crystal silicon substrate, function elements for driving the electricity-heat conversion elements such as a transistor array are arranged outside the silicon substrate as a drive circuit for the electricity-heat conversion elements, and the connection between the electricity-heat conversion elements and the transistor array is made by wire bonding.
For the purposes of providing a simplified structure to be considered for the above head constitution, reducing the failure which may arise in the manufacturing process, or providing the uniform characteristic or improved reproducibility for each element, an ink jet recording apparatus is known which has a recording head having electricity-heat conversion elements and function elements provided on the same substrate, as proposed in Japanese Laid-open Patent Application No. 57-72867.
FIG. 16 is a typical cross-sectional view showing a part of a recording head substrate as constituted above. 901 is a semiconductor substrate composed of single crystal silicon. 902 is an epitaxial region of N-type semiconductor, 903 is an ohmic contact region of N-type semiconductor having a high impurity density, 904 is a base region of P-type semiconductor, and 905 is an emitter region of N-type semiconductor having a high impurity density, whereby a bipolar transistor 920 is formed of them. 906 is an oxide silicon layer serving as a heat storing layer and an insulating interlayer, 907 is a heating resistive layer, 908 is a wiring electrode made of aluminum (Al), 909 is an oxide silicon layer as a protective layer, whereby a recording head base body 930 is formed of them. Here, 940 serves as a heating portion. A recording head is constructed by a ceiling plate and the liquid channels formed on this base body 930.
By the way, the structure as described above may be superior, but there is yet much room for improvement to meet the high speed driving, the energy saving, the high integration, the lower costs, and the high reliability which have been strongly demanded for the recording apparatus in recent years.
First, the recording head having high reliability must be provided at low price. To this end, with the conventional recording head, the heating portion of heater and a driving portion and the ink nozzle portion are separately formed, after which they are bonded together in alignment. However, with this method, the heating center of heater may be offset from the center of nozzle, more likely resulting in the degraded performance of the recording head. To effect the fast driving stably, it is important to stabilize the bubbling performance of the ink. Also, it is necessary for the fast driving to make the bubbling center of ink nozzle closer to the nozzle head. For this purpose, the use of higher resistive heater and the effective use of calorific value are required.
The heater provided on the silicon substrate has its calorific value partly leaking away to the silicon substrate, and is required to generate more heat for the bubbling. To prevent such leaking of the heat to the silicon substrate, a lower heat conductive material must be formed thick under the heater. Normally, a silicon oxide film is used under the heater, in which it takes much time to form the thick silicon oxide film.
Also, in the ink jet head using heating elements, it is increasingly demanded, with the higher function of the driving elements, that the heat generated by the heating elements is prevented from passing to the driving elements.